Magnetic alloy



. alloy which is workable.

Patented May 17, 1932 UNITED STATES PATENT OFFICE ALBERT A. FREY, OF FOREST HILLS, PENNSYLVANI A, .AND GUER NEY H. COLE, OF MID- DLETOWN, OHIO, A SSIGNORS TO WESTINGHOUSE ELECTRIC AND MANUFACTURING COMPANY, A. CORPORATION OF PENNSYLVANIA i MAGNETIC ALLOY No Drawing.

Our invention relates to alloys-and more particularly to magnetic alloys containing iron, silicon and arsenic.

The principal object of our invention is to provide ductile alloy containing iron, silicon and arsenic which, when tested magnetically, has a low core loss.

Another object of our invention is to provide an alloy containing iron, silicon and arsenic that shall have higher ductility than iron-silicon alloys and which, when utilized in cores for transformers, is characterizedby having a total watt loss as low as .92 watts per kilogram, when tested-at an induction of 10,000 gausses and at cycles.

A further object of our invention is to provide cores for electrical apparatus, such as transformers, generators and the like, comprising rolled and annealed laminations comprising an alloy of iron, silicon and arsenic. Iron-silicon alloys have heretofore been extensively utilized in the cores of electrical apparatus, such as transformers. When more than 4 per cent silicon, however, is uti lized, the alloy becomes brittle and is difli cult to roll and punch. Consequently, the amount of silicon which may be utilized is limited. It is essential, in producing magnetic materials, that the material utilized shall have a high electrical resistance in order to reduce eddy-current losses. Silicon is very effective in this respect but, since the amount of this element which may be utilized is small, it is impossible to reduce the eddy current lossbeyond acertain limit and still provide an \Ve have made the discovery that the electrical properties of iron silicon alloys may be considerably improved by the addition of .1 per cent to 6 per cent of arsenic, whereby an alloy is produced which may be rolled and punched. \Vhen properly annealed, our improved alloy has a higher maximum permeability than iron-silicon alloys and is. charilCtGIlZed by having an especially low core oss.

In practicing our invention, we melt iron in a suitable furnace, such as an electric induction furnace, which is maintained at a temperature of from2700 F. to 2900 F.v

. tainin from 1 Application filed J'u1y-17,' 1931. Serial No. 551,548.

At this temperature, arsenic may be addedto V iron, silicon is added, either as pure silicon or ferrosi'licon. We prefer, however, to add the arsenic and silicon to the molten iron in one operation, as the iron is being poured into the ladle by the addition of an alloy or compound of arsenic, siliconand iron. The alloy may then be cast into ingots of any desired form to be subsequently rolled into bars or sheets, according to the usual practice.

The amount of arsenic and silicon which are added tothe iron will depend upon the magnetic and mechanical,characteristics de shed and, as a rule, will vary between .1 per cent to 6 per cent of arsenic.

The amount of arsenic utilized will de end upon the magnetic characteristics desired. If a high saturation value isrequired, a small amount, say not more than A, per cent, is sufficient. Arsenic increases the resistance of the alloy without increasing the brittleness and, consequently, when a comparatively large amount of arsenic is utilized, the core loss is decreased.

Arsenic, however, is very difiicult to introduce into the alloy because of its high volatility at the alloying temperature of the iron. We, thenefore, prefer to utilize an alloy con- D per cent to 2 per cent, by weight, of arsenic. The amount of silicon which may be added is limited because large amounts increase the brittlenessof the alloy a d render it unforgeable. The amount of silicon, therefore, should be maintained withes high fluidity in the molten state and may be readily cast.

After the alloy is cast-and rolled, in the 9 manner specified, it is subjected to a suitable annealing operation. Asuitable annealing operation may conslst 1n heating the rolled sheets to a temperature of 900 to 1100 C."

in air, a neutral atmosphere or in hydrogen 'for a period of from 2 to 8 hours and then cooling in the furnace.

In preparing laminations for electrical apparatus, such as transformers, however, we prefer to anneal the sheet material in air, a neutral atmosphere or hydrogen for a-period of several days at a temperature of 900 or 1100 C- The material is cooled in the furnace, the laminations are punched and the material is then re-annealed for a similar period at a temperature of 700 to 800 G.

Our preferred alloy, when properly annealed, has exceptionally good magnetic characteristics. 7 For example, an alloy containing from 1 per cent to 2 percent, by weight, of arsenic and from 3.5 per cent to 4 per cent, by weight, of silicon, in the form of a rolled sheet, had a core loss of only .92 watts per kilogram when tested at an induction of 10,000'gausses and cycles. I

The following table shows the actual analysis andv core losses foralloys of different compositions afterthey have been rolled into sheet form andannealed.

W (Watt Wu (Watt loss per kg. loss per kg. at 60cycles at 60 cycles Silicon Arsenic Iron at an inat an induction duction of 10,000 of 14,000. gausses) gausses) Our improved magnetic alloys are superior to iron-silicon alloys because a higher content of combined arsenic and silicon may be utilized than of silicon alone, without increasing the brittleness of the alloy. A ductile alloy having a higher resistance than iron-silicon alloys may thus be formed. This is highly essential because it decreases the core loss. The arsenic also acts as a purifier of the alloy,'while it is in the. molten state, because it reacts with the non-metallic inclusions forming a compound which floats to the surface of the molten alloy and may be removed. Our improved alloy is superior to iron-arsenic alloys because sheets formed from such alloys have the tendency to adhere to each other and to the rolls when a plurality of them are rolled according to the hot-pack rolling process,

While we have disclosed our invention in considerable detail and have given specific examples, it will be understood that the examples are to be construed as illustrative and not by way of limitation. For example, it will be understood that the alloy will 'contain a small'amount of impurities. It is preferred that the amount of magnetically detrimental impurities shall be less than .02 per cent. Electrolytic iron or a high grade com-,

mercial iron, such as Armco iron, may be utllized. Other elements or'impurlties may be present, provided they are not magnetictions shall be imposed asare indicated in the appended claims. I

\Ve claim as our invention: a

1. Aniagnetic alloy comprising iron as a major constituent and siliconand arsenic as minor constituents.

2. A magnetic alloy comprising iron as a major-constituent and from l per cent to 6 per cent, by weight, of silicon and from .1 per cent to 6 per cent, by weight, of arsenic.

3. 'A magnetic alloy'comprising ironas a major constituent and from 1 per cent to 6 per cent. by weight, of a silicon compound or alloy and from .1 per cent to 6 per cent, by weight, of an arsenic compound or alloy. 4

- .4. A magnetic alloycomprising' iron as a major constituent and a combined arsenic and i I silicon content of from. .2 per cent to 12 per cent. l

'5 A magnetic alloy comprising ironas a ma or constituent and from '3 per cent to 4 per cent, by weight, of silicon and from .5 per cent to 2 per cent, by weight, of ZLISBIIHL.

6. A magnetic ductile alloy comprising iron as a majorconstituent and from 1 per cent to 2 per cent, by weight, of arsenic and from 3.5 per cent to 4. per cent, by weight, of

silicon, saidalloy having a core loss of less than one watt per kilogram at an induction of 10,000 gausses.

.7. A magnetic alloy comprising at least 'per cent, by weight, of iron, from .5 per cent to 2 per cent, by weight, of arsenic and from 1 percent to 4 per cent, by wei ht, of silicon, said alloy having a core loss 0 less than one watt per kilogram when tested at an induction of 10,000 gausses and (SO cycles.

8. An article of man ufacture comprising a rolled sheet of magnetic material composed .of an alloy comprising at least 90% iron, .1

to 6% silicon and .1% to 6% arsenic.

'9. A lamination forv electical apparatus comprising a rolled sheet of magnetic material composed of an alloy comprising at least 90% iron, 6% arsenic.

10. A transformer core composed of a pluralit y of laminations of magnetic sheet material, each of said sheets being formed of an alloy comprising at least 90% iron, .l% to 6% silicon and .1% to 6% arsenic.

In testimonywhereof, we have hereunto subscribedour names.

ALBERT A. FREY.

GUERNEY H. COLE.

.1% to 6% silicon and .1% to 

